1. Field of the Invention
The present invention relates generally to location systems, and more specifically to a location system in which a number of positioning methods are selectively used depending on accuracy requested by a LCS (LoCation Service) client terminal.
2. Description of the Related Art
In the location system as standardized by 3GPP (3rd Generation Partnership Project) TS 25.305, a number of positioning methods are used, including Cell-ID method, OTDOA (Observed Time Difference Of Arrival), and A-GPS (network-assisted Global Positioning System). The system is made up of a core network and a W-CDMA radio access network (RAN) in which the radio network controller (RNC) is responsible for controlling a number of base stations to establish connections to mobile terminals. When a client terminal transmits a location request to the location system by specifying accuracy of the location of a target mobile terminal or UE (user equipment) terminal, the request is passed through the core network to the RNC, one of the positioning methods is selected according to the requested accuracy and/or the positioning capability of the target UE terminal to perform measurement and position calculation and returns a location report message to the client terminal.
Since all traffic to and from mobile terminals is concentrated on the RNC and the selection of a positioning method is a complex, time-consuming process, the processing burden is significant when the network is under heavy traffic load.
In addition, no consideration has been taken of other factors to select a positioning method, such as the environment of the target UE terminal. As a result, if a target mobile user is located in a place such as underground shopping areas where GPS satellites are not observable and if the RNC selects A-GPS according to the requested accuracy, the location request results in a useless traffic, unnecessarily consuming network resources.